diff --git a/src/backend/InvenTree/InvenTree/api.py b/src/backend/InvenTree/InvenTree/api.py
index 4610157e56..f76b3bea3f 100644
--- a/src/backend/InvenTree/InvenTree/api.py
+++ b/src/backend/InvenTree/InvenTree/api.py
@@ -18,10 +18,11 @@ from rest_framework.response import Response
 from rest_framework.serializers import ValidationError
 from rest_framework.views import APIView
 
+import common.models
 import InvenTree.version
 import users.models
 from common.settings import get_global_setting
-from InvenTree import helpers
+from InvenTree import helpers, ready
 from InvenTree.auth_overrides import registration_enabled
 from InvenTree.mixins import ListCreateAPI
 from InvenTree.sso import sso_registration_enabled
@@ -710,6 +711,9 @@ class MetadataView(RetrieveUpdateAPI):
         """Return the model type associated with this API instance."""
         model = self.kwargs.get(self.MODEL_REF, None)
 
+        if ready.isGeneratingSchema():
+            model = common.models.ProjectCode
+
         if 'lookup_field' in self.kwargs:
             # Set custom lookup field (instead of default 'pk' value) if supplied
             self.lookup_field = self.kwargs.pop('lookup_field')
diff --git a/src/backend/InvenTree/InvenTree/api_version.py b/src/backend/InvenTree/InvenTree/api_version.py
index 7dfc9bffb2..0c6f105590 100644
--- a/src/backend/InvenTree/InvenTree/api_version.py
+++ b/src/backend/InvenTree/InvenTree/api_version.py
@@ -1,12 +1,15 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 330
+INVENTREE_API_VERSION = 331
 
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 
 INVENTREE_API_TEXT = """
+v331 - 2025-04-01 : https://github.com/inventree/InvenTree/pull/9437
+    - Set correct types on various formerly-string PK fields as well permissions
+    - Include metadata request and response types
 
 v330 - 2025-03-31 : https://github.com/inventree/InvenTree/pull/9420
     - Deconflict operation id between single and bulk destroy operations
diff --git a/src/backend/InvenTree/build/api.py b/src/backend/InvenTree/build/api.py
index 9fb43d1c87..0720407fd0 100644
--- a/src/backend/InvenTree/build/api.py
+++ b/src/backend/InvenTree/build/api.py
@@ -8,6 +8,8 @@ from django.urls import include, path
 from django.utils.translation import gettext_lazy as _
 
 from django_filters import rest_framework as rest_filters
+from drf_spectacular.utils import extend_schema_field
+from rest_framework import serializers
 from rest_framework.exceptions import ValidationError
 
 import build.admin
@@ -103,6 +105,7 @@ class BuildFilter(rest_filters.FilterSet):
         label=_('Category'),
     )
 
+    @extend_schema_field(serializers.IntegerField(help_text=_('Category')))
     def filter_category(self, queryset, name, category):
         """Filter by part category (including sub-categories)."""
         categories = category.get_descendants(include_self=True)
@@ -114,6 +117,7 @@ class BuildFilter(rest_filters.FilterSet):
         method='filter_ancestor',
     )
 
+    @extend_schema_field(serializers.IntegerField(help_text=_('Ancestor Build')))
     def filter_ancestor(self, queryset, name, parent):
         """Filter by 'parent' build order."""
         builds = parent.get_descendants(include_self=False)
@@ -293,6 +297,7 @@ class BuildFilter(rest_filters.FilterSet):
         label=_('Exclude Tree'),
     )
 
+    @extend_schema_field(serializers.IntegerField(help_text=_('Exclude Tree')))
     def filter_exclude_tree(self, queryset, name, value):
         """Filter by excluding a tree of Build objects."""
         queryset = queryset.exclude(
diff --git a/src/backend/InvenTree/common/serializers.py b/src/backend/InvenTree/common/serializers.py
index 896c75d9e3..2c4e5403ef 100644
--- a/src/backend/InvenTree/common/serializers.py
+++ b/src/backend/InvenTree/common/serializers.py
@@ -6,6 +6,8 @@ from django.urls import reverse
 from django.utils.translation import gettext_lazy as _
 
 import django_q.models
+from drf_spectacular.types import OpenApiTypes
+from drf_spectacular.utils import extend_schema_field
 from error_report.models import Error
 from flags.state import flag_state
 from rest_framework import serializers
@@ -28,6 +30,7 @@ from plugin import registry as plugin_registry
 from users.serializers import OwnerSerializer, UserSerializer
 
 
+@extend_schema_field(OpenApiTypes.STR)
 class SettingsValueField(serializers.Field):
     """Custom serializer field for a settings value."""
 
@@ -35,7 +38,7 @@ class SettingsValueField(serializers.Field):
         """Return the object instance, not the attribute value."""
         return instance
 
-    def to_representation(self, instance):
+    def to_representation(self, instance) -> str:
         """Return the value of the setting.
 
         Protected settings are returned as '***'
@@ -47,7 +50,7 @@ class SettingsValueField(serializers.Field):
         else:
             return str(instance.value)
 
-    def to_internal_value(self, data):
+    def to_internal_value(self, data) -> str:
         """Return the internal value of the setting."""
         if data is None:
             return ''
diff --git a/src/backend/InvenTree/company/api.py b/src/backend/InvenTree/company/api.py
index b9cdd44835..97c04117dd 100644
--- a/src/backend/InvenTree/company/api.py
+++ b/src/backend/InvenTree/company/api.py
@@ -306,7 +306,7 @@ class SupplierPartFilter(rest_filters.FilterSet):
         label=_('Company'), queryset=Company.objects.all(), method='filter_company'
     )
 
-    def filter_company(self, queryset, name, value):
+    def filter_company(self, queryset, name, value: int):
         """Filter the queryset by either manufacturer or supplier."""
         return queryset.filter(
             Q(manufacturer_part__manufacturer=value) | Q(supplier=value)
diff --git a/src/backend/InvenTree/order/api.py b/src/backend/InvenTree/order/api.py
index 11e31cca0d..f09a04e0e2 100644
--- a/src/backend/InvenTree/order/api.py
+++ b/src/backend/InvenTree/order/api.py
@@ -11,8 +11,11 @@ from django.http.response import JsonResponse
 from django.urls import include, path, re_path
 from django.utils.translation import gettext_lazy as _
 
+import rest_framework.serializers
 from django_filters import rest_framework as rest_filters
 from django_ical.views import ICalFeed
+from drf_spectacular.types import OpenApiTypes
+from drf_spectacular.utils import extend_schema_field
 from rest_framework import status
 from rest_framework.response import Response
 
@@ -289,6 +292,7 @@ class PurchaseOrderFilter(OrderFilter):
         method='filter_part',
     )
 
+    @extend_schema_field(rest_framework.serializers.IntegerField(help_text=_('Part')))
     def filter_part(self, queryset, name, part: Part):
         """Filter by provided Part instance."""
         orders = part.purchase_orders()
@@ -301,6 +305,9 @@ class PurchaseOrderFilter(OrderFilter):
         method='filter_supplier_part',
     )
 
+    @extend_schema_field(
+        rest_framework.serializers.IntegerField(help_text=_('Supplier Part'))
+    )
     def filter_supplier_part(
         self, queryset, name, supplier_part: company.models.SupplierPart
     ):
@@ -520,6 +527,9 @@ class PurchaseOrderLineItemFilter(LineItemFilter):
         label=_('Internal Part'),
     )
 
+    @extend_schema_field(
+        rest_framework.serializers.IntegerField(help_text=_('Internal Part'))
+    )
     def filter_base_part(self, queryset, name, base_part):
         """Filter by the 'base_part' attribute.
 
@@ -735,6 +745,7 @@ class SalesOrderFilter(OrderFilter):
         queryset=Part.objects.all(), field_name='part', method='filter_part'
     )
 
+    @extend_schema_field(OpenApiTypes.INT)
     def filter_part(self, queryset, name, part):
         """Filter SalesOrder by selected 'part'.
 
@@ -1108,6 +1119,7 @@ class SalesOrderAllocationFilter(rest_filters.FilterSet):
         queryset=Part.objects.all(), method='filter_part', label=_('Part')
     )
 
+    @extend_schema_field(rest_framework.serializers.IntegerField(help_text=_('Part')))
     def filter_part(self, queryset, name, part):
         """Filter by the 'part' attribute.
 
@@ -1335,6 +1347,7 @@ class ReturnOrderFilter(OrderFilter):
         queryset=Part.objects.all(), field_name='part', method='filter_part'
     )
 
+    @extend_schema_field(OpenApiTypes.INT)
     def filter_part(self, queryset, name, part):
         """Filter by selected 'part'.
 
diff --git a/src/backend/InvenTree/part/api.py b/src/backend/InvenTree/part/api.py
index 73f0c2f559..6fad282fe9 100644
--- a/src/backend/InvenTree/part/api.py
+++ b/src/backend/InvenTree/part/api.py
@@ -1441,6 +1441,7 @@ class PartRelatedFilter(rest_filters.FilterSet):
         queryset=Part.objects.all(), method='filter_part', label=_('Part')
     )
 
+    @extend_schema_field(serializers.IntegerField(help_text=_('Part')))
     def filter_part(self, queryset, name, part):
         """Filter queryset to include only PartRelated objects which reference the specified part."""
         return queryset.filter(Q(part_1=part) | Q(part_2=part)).distinct()
diff --git a/src/backend/InvenTree/users/serializers.py b/src/backend/InvenTree/users/serializers.py
index 15cb5fc796..a6ddea331d 100644
--- a/src/backend/InvenTree/users/serializers.py
+++ b/src/backend/InvenTree/users/serializers.py
@@ -52,7 +52,7 @@ class GroupSerializer(InvenTreeModelSerializer):
 
     permissions = serializers.SerializerMethodField(allow_null=True)
 
-    def get_permissions(self, group: Group):
+    def get_permissions(self, group: Group) -> dict:
         """Return a list of permissions associated with the group."""
         return generate_permission_dict(group.permissions.all())
 
@@ -109,7 +109,7 @@ class RoleSerializer(InvenTreeModelSerializer):
         return generate_permission_dict(permissions)
 
 
-def generate_permission_dict(permissions):
+def generate_permission_dict(permissions) -> dict:
     """Generate a dictionary of permissions for a given set of permissions."""
     perms = {}